Radiation has long been known to damage biological tissues and cells. Initial deposition of energy in irradiated cells occurs in the form of ionized and excited atoms or molecules distributed at random throughout the cells. The ionizations cause chemical changes in the exposed area, producing highly unstable charged or “ionized” molecules. These rapidly undergo chemical changes, producing free radicals that react with cellular components and lead to permanent damage.
As an immediate consequence of radiation damage, cells can undergo apoptosis, dying in interphase within a few hours of irradiation. Typical morphologic changes include loss of normal nuclear structure and degradation of DNA. DNA damage is important in triggering programmed cell death; membrane damage and signaling pathways are also thought to be involved.
A sufficiently high dose of radiation will inhibit mitosis. Inhibition of cellular proliferation is a mechanism by which radiation kills most cells. As radiation kills cells by inhibiting their ability to divide, its effects in living organisms occur primarily in tissues with high cell turnover or division rates, characterized by high proliferative activity.
The development of effective radioprotectant molecules is of great importance to populations potentially subjected to accidental, intentional or military exposure to radiation, including ionizing radiation.